Noxious Gearhulk, a.k.a. Graalhulk, is pretty much everything you want for a grindy deck. For 6 mana it creates a reasonable threat, kills a creature—any creature—and gains you some life. Heck, it's not even that bad against an Emrakul that controls your turn! So needless to say, I am pretty high on this card.
It's a 5/4 menace, making it adept at killing planeswalkers, since it's so hard to block. A deck that wants to run Graalhulk will most likely have plenty of other removal, making the required double-block much more unlikely. Even Emrakul has a hard time stopping the Noxious Gearhulk, since most of the time that Emrakul resolves, she's the only creature able to block.
When it enters the battlefield, it destroys a creature. Creatures with an enters-the-battlefield trigger that deals with a creature have a storied history from Nekrataal to Shriekmaw to Murderous Redcap to Flametongue Kavu. Each of these all-stars' abilities were somewhat conditional, and this Gearhulk doesn't even put a restriction on its target. That makes it even better than merely a 2-for-1, because both cards are affecting the board in a significant way. Divination is a 2-for-1, but it doesn't affect the board in the slightest. Both “cards earned” by Noxious Gearhulk are on the board—both in the 5/4 body it creates and the creature it kills. An effect like this is especially important given Standard's change of pace over the last few years, where winning is determined by controlling the board to create velocity rather than raw card advantage.
When you have determined how much of an impact the card will have on a game, you can then set a value to the additional life gain. For example, if I can Nourish, the power level of the play is flat zero since it doesn't create card advantage or impact the board in any sense. If I cast Siege Rhino, which is a 4/5 trample that deals 3 damage to them, or Sphinx's Revelation which draws X cards, the impact is enormous! To sum it up, the more chance the card has to win the game after it resolves, the more value the life gain has, because it protects you from the only chance that you will lose the game—if you are “cheesed out” of the game with a couple of burn spells or a big attack. So because Noxious Gearhulk gives you a sizable advantage and the power level is high but doesn't win on the spot, the extra life gain is becomes a critical addition to the card.
The last, slightly important attribute of the card is that it is an artifact creature. It makes Emrakul, the Promised End cheaper and adds value to cards that care about artifacts, such as Glint-Nest Crane.
I can think of many shells for Noxious Gearhulk because it's just such a powerful card, but mostly in grindy midrange or control decks, because it does cost 6 mana to cast. Since it has an enters-the-battlefield effect, it would be nice to reuse it. You can do that either with something like Eldrazi Displacer or get it back after it goes to your graveyard—which is the way I'm leaning with Grapple with the Past and Liliana, the Last Hope. No longer do we have to play a conditional Gilt-Leaf Winnower or beef up our late game with Woodland Bellower. Rejoice!
BG Delirium Gearhulk
Next up, Bro(w)Hulk!